Analog-to-digital converters (ADCs) are employed in a variety of electronic systems including computer modems, wireless telephones, satellite receivers, process control systems, and the like. Such systems demand cost-effective ADCs that can efficiently convert an analog input signal to a digital output signal over a wide range of frequencies and signal magnitudes with minimal noise and distortion.
An ADC typically converts an analog signal to a digital signal by sampling the analog signal at pre-determined sampling intervals and generating a sequence of binary numbers that is a digital representation of the sampled analog signal. Commonly used types of ADCs includes flash ADCs.
A conventional flash ADC typically requires 2n−1 comparators, where n is the number of bits of the flash ADC. Since the comparators can process an input signal concurrently, conventional flash ADCs are desirable for high-speed applications. However, as the resolution of the flash ADC increases to accommodate high-speed applications, so does the number of comparators, the die area and the power consumption needed to accommodate the comparators. For example, while a four-bit flash ADC typically needs only 15 comparators, a eight-bit flash ADC typically requires 255 comparators.